For some time now filament string vegetation cutters have been used for grass trimmers, lawn mowers, and weed removers. Such string trimmers are attached to and extend from a balanced mower head or framework which is centrally mounted on a shaft which is rotated by means of an electric or gas motor. Typical examples are disclosed in U.S. Pat. Nos., 4,112,653: 5,023,998; 4,513,563; 4,962,630; 4,295,324; 4,461,138; 4,819,416; and 4,962,635.
U.S. Pat. No. 5,023,998 discloses a four quadrant string vegetation cutter where the quadrants are offset to create a protrusion that acts as a rock guard. U.S. Pat. Nos. 4,295,324, and 4,962,630 disclose air foils disposed on line holder arms to lift the grass or vegetation upward prior to its being cut. Since a rock guard requires a full diameter or over diameter projection dish, it would seem to be incompatible with air foil means to cause upward drafts. In addition the air toils of the prior art have been disposed on the leading edge of the support line holder arms where they are prone to damage by rocks or other projections of the terrain.
Accordingly, it would be desirable to have a string trimmer retaining means that incorporated both a rock guard and an air foil means to cause upward drafts. It would also be desirable if the string trimmer retaining means incorporated the air foil means on the trailing edge of its support arms so as to protect the air foil edge from damage from abrasive particles and abrupt edges encountered when traversed over rough terrain. It would also be desirable to have a second air foil means disposed on a rock guard annular disk to direct air and entrained vegetation outwardly. It would further be desirable if the rock guard had an annular shape and circumvented and attached to the outer ends of radial arms so as to provide a unibody integral construction of the retaining means framework for strength/unit weight. It would also be desirable if the annular shaped rock guard is made of a dense material or is adapted to carry dense material distributed over its circumference so as to simulate a flywheel means for use with the motor driven shaft of the vegetation cutting apparatus.